Patent GB-1294291-A (GB)
Title: Method and system for establishing a correct lead when firing at a moving target
Inventor: ERHARD RUNE TORSTEN ISIDOR
IPC: F41G3/06
Filed: 1970-01-02
Abstract: 1294291 Sights and methods of sighting BOFORS AB 2 Jan 1970 [3 Jan 1969] 270/70 Heading F3C [Also in Division G4] In a method for providing a correct lead when firing a projectile at a moving target, the sight is maintained pointed directly at the target, and the angular velocity of the line of sight is integrated over a predetermined limited interval during which the direction of fire of the weapon is moved uniformly with the line of sight, whereafter the line of sight and the direction of fire are deflected from each other by an angle proportional to the result of integration and in such sense that the direction of fire will lead the line of sight. As shown, a manually operated lever 5 controlling signal sources 51 and 52 determines the angular velocity of the gun barrel in azimuth and in elevation, respectively, by means of the servo motors M1, M2 comparators C1, C2, amplifiers F1, F2, and tachogenerators T1, T2, the signals from which are fed back in opposition to the'comparators. A sighting instrument mounted on the gun barrel is similarly movable in azimuth and elevation with respect to the barrel by servo motors M3 and M4 which have predetermined starting positions in which the line of sight is parallel to to the barrel. Potentiometers P1 and P2 feed back signals to comparators C3 and C4 which are proportional to the angle of rotation of the motors, whereby the motors rotate the sighting instrument through angles proportional to control signals from amplifiers F3 and F4, respectively and inversely proportional to the signal-which is proportional to the mean velocity of the projectile-from amplifier F5. When the line of sight shown by the dotted line in Fig. 3, has been accurately aimed at the moving target, shown by the full line, a timer T having a time span # proportional to the range to the target, is energized, at time # 1  Fig. 3, to close switches K1 and apply the tachogenerator signals from T1 and T2 to integrators I1 and I2, for computing the lead angles in azimuth and elevation required due to movement of the target, a correcting factor involving the superelevation being provided at the output of amplifier F6, and another involving projectile rotation and wind forces being provided at the output of amplifier F7 at the termination # 2  of the timer interval, switches K1 are opened and switches K2, K4, and K5 closed to apply the integrated signals and correcting factors to amplifiers F3 and F4, which then rotate motors M3 and M4 to deflect the line of sight, to lag the target, through the required lead angle # t . Thereafter, lever 5 is again operated to aim the sight at the target, and thereby deflect the gun barrel, shown by the dash-dot curve, through the required lead angle, whereafter firing can commence. In a modified arrangement, which, avoids the manual reaiming of the sight, tachogenerators T3 and T4, generating signals proportional to the rates of rotation of servomotors M3 and M4, are coupled comparators C1 and C2, to apply the signals to motors M1 and M2 in a sense assisting the control signals from the signal generators S1 and S2, whereby when the motors M3 and M4 start to rotate the gun barrel is given increased azimuthal and elevational angular velocities, such that the sight remains aimed at the target and the barrel is deflected through the required lead angle. If the sighting instrument is not mounted on a layable portion of the gun, the servomotors for the latter are supplied with control signals derived from position detectors coupled to the servomotors of the sighting instrument.